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BIO233 > Viruses > Flashcards

Viruses Flashcards

1
Q

Most abundant microbes on earth

A

Virus

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2
Q

What does it mean that a virus is an “obligate intracellular parasite”

A

Must exist within a cell

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3
Q

What kinds of cells do viruses infect

A

Infect all kinds of cells (prokaryotes and eukaryotes)
Specific, eukaryote virus vs prokaryote virus

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4
Q

What kind of cells do viruses have

A

Acellular (not all the characteristics of the cell) or subcellular (missing stuff that constitutes thecell entities

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5
Q

Why are viruses not considered living

A

Acellular and cannot reproduce independantly

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6
Q

Size of virus

A

Extremely small: 30nm (poliovirus) to 300nm (vaccinia virus) in diameter

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7
Q

Structure of virus

A

Outside: protein coat (capsid)
Some have lipd envolope (envolope virus
No evnolpe = naked virus
Small genomes, very few genes (3-100s)
DNA or RNA (NEVER BOTH)
Few proteins, NO ribosomes or ATP-generating mechanism

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8
Q

Compare viruses and bacteria

A

Viruses do not contain both RNA and DNA

Bacteria does

Viruses are not sensitive to antibiotics while bacteria are

Viruses are sensitive to interferons

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9
Q

Capsid

A

protein coat that enclose and protect genetic material
Some of have external lipid covering, some do not
Capsid made from identical subunits called capsomers

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10
Q

Viruses classified into several morphological types

A

Helical
Polyhedral
Complex
Envoloped

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11
Q

Helical viruses

A

Long rods, cylindrical capsid; rigid OR flexible
DNA/RNA within a hollow, cylindrical capsid (Helical structure_
Ex. Ebola or rabies

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12
Q

Polyhedral viruses

A

Many anim, plant and bacteria viruses tend to be this type
Icosahedron shape: 20 trianglualr aces and 12 corners
Each face forms and equilateral triangle
Ex. Adenovirus, poliovirus

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13
Q

Complex viruses

A

Complicated structures (i.e. bacteriophage)
Capsid head is polyhedral and the tail sheath is helical
Other structures such as tail fibers (proteins) and pin (for injecting DNA)
Ghost virus: Have already injected DNA into bacterial cell

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14
Q

Are Helical, polyhedral, and complex viruses normally naked or enveloped?

A

Most are naked

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15
Q

Envoloped virus

A

Envolope: composed of lipids, proteins and carbohydrates
Derived from host
May be covered with spikes
Glycoproteins fro attachment
Ex.
SARS Coronavirus
Influenza virus
Herpesvirus

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16
Q

How do viruses avoid recognition

A

Viruses change spike composition to avoid antibody recognition

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17
Q

Naked viruses (plus examples)

A

No lipid coat outside the capsid
Ex. Rhinovirus
Polivirus
Norwalk

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18
Q

Where do viruses gr ow

A

Grow in living cells
Bacteriophages from plaques on a lawn of uninfected bacteria
Animal viruses are grown in living animals, embryonic eggs, cell cultures etc.

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19
Q

What is the viruses growth cycle called

A

One-step growth curve

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20
Q

Eclipse period:

A

The initial period following the virus entering a host, where the viruses enter the host cells, and so none are detected in circulation
After the eclipse, virions are released from the host cell
Known as the one-step growth curve

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21
Q

Two major cycles of viral replication

A

Lytic cycle (Reproduction of more viruses) Transcription and translation.
Lysogenic cycle (incorporation of DNA into cell DNA)
Viral DNA incorporated into cell genome

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22
Q

6 steps of viral reproduction

A

Attatchement
Penetration
Transcription (DNA is transcribed into RNA and used to make proteins from ribosomes)
Biosynthesis (Viral components (proteins) are assembled)
Maturation
Lysis

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23
Q

How do regular bacterial cells produce sickness

A

Only cells that have picked up extra genes can produce sickness

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24
Q

Lytic cycle

A

Attatchment and penetration
Biosynthesis, beginning with replication or transcription and translation
Synthesising proteins and assembly into viral particles
Cell lyses and releases viruses

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25
Q

Lysogeny cycle

A

Cell can continue it’s life indefinitely
Incorpration of phage DNA into bacteria genome = phage conversion, therefore, host acquirees new properties
Some pathogenic E. coli have picked up extra genes from viruses
Diphtheria toxin corynebacterium diphtheria
Many pathogenic bacteria are innocent, but they have been hijacked by viruses to make them pathogenic

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26
Q

Multiplication of animal viruses

A

Attatchment: Attachment to cell membrane
Penetration: endocytosis (Eukaryote grabs whole viral particle and internalizes it) or fusion
Uncoating: Require viral or host enzymes to break up coat on outside to expose genome
Biosynthesis: The Genome of virus can be used by animal cells to make mRNA, proteins etc. using nucleic acid and oriteinb synthesis
Maturation: Mucleic acid and capsid asembly
Release: Budding (envoloped viruses) or rupture(non-envoloped viruses)
Multiplication of animal viruses

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27
Q

ways a virus can enter a host cell

A

Endocytosis or fusion for animal viruses

DNA injection by bacteriophages

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28
Q

What is the purpose of encoating the virus once within the cell?

A

To release genetic material in the case of animal cells

Unneccessary in bacteria cells

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29
Q

What is a part of the biosynthesis stage

A

Proteins are made based on the mRNA code

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30
Q

What occurs in the maturation stage

A

Involves the assembly of new viral particles (packaging the DNA/RNA into protein coat)

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31
Q

Two ways that the “release phase” can occur

A

Budding (if it is an envolope virus) or lysis for naked viruses

Host cell is always lysed in bacteria

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32
Q

Where do the steps of replication occur in bacteria and animal cells

A

Replication, and transcription takes place in nucleus and translation (mRNA) occurs in the cytoplasm

ALL of these 3 occur in cytoplasm in the bacteria cells

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33
Q

Storage form of genetic info is always

A

DNA

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34
Q

How are transcription, translation and protein synthesis connected

A

Viral DNA (Genetic code) transcribed to mRNA (same language, but placed in different form) (Code in transit) Translated to protein by ribosomes (performs functions nd activities and structural support for the cell.\

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35
Q

Is replication connected to transcription/translation

A

An independent event, not needed for transcription

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36
Q

What is the virus objective in invading a host cell

A

Multiplication

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37
Q

What enzyme is involved in DNA replication?

A

DNA dependent DNA polymerase

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38
Q

What is transcription, and what enzyme is involved?

A

Transcription is the copying of one DNA strand into mRNA, done my DNA dependent RNA Polymerase

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39
Q

What is translation, and which organelle is involved?

A

mRNA moved to nucleus, ribosomes read info on mRNA, translate to the language of proteins, and then make the proteins (protein synthesis)

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40
Q

When does translation begin in bacteria cells?

A

Even before mRNA has been completely formed, Ribosomes can begin transcription bc there is no nucleus separation

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41
Q

What is the DNA template strand?

A

Aka the negative strand or Anti-sense strand

The unzipped strand of DNA from which the mRNA is made from (mirrored from)

42
Q

RNA vs DNA

A

RNA: Ribose: One extra oxygen, single stranded, U instead of T

Deoxyribose: missing one oxygen, Double helix, no U but T

43
Q

What is the mRNA strand that is transcribed from the template DNA strand called?

A

The Sense mRNA or Positive strand

44
Q

What is the non-template strand of DNA called?

A

AKA sense strand OR positive strand of DNA

45
Q

How many strands of DNA are being used at once in viral replication (assuming there is DNA present)

A

one, since it will coordinate with specific proteins, and the non template strand is the template for completely different proteins

46
Q

What is negative mRNA?

A

AKA Antisense mRNA (-)
Made from the sense mRNA (+)

Exact copy (besides U instead o T) of antisense DNA

47
Q

How many DNA/RNA do viruses caryy

A

Single, double, RNA or DNA

48
Q

What must viruses with a single strand of DNA do to start replication process within a host cell?

A

The virus must have info/genes that call for the enzyme polymerase to use single-stranded DNA to make double-stranded DNA

49
Q

Which type of virus carry strand(S) if genetic material that can be used immediately for protein synthesis

A

mRNA(+)

50
Q

What happens if a virus carries a double stranded RNA

A

the host cell must separate the two strands and use the sense strand for protein synthesis

51
Q

What is multiplied in viral replication?

A

The viral genome

52
Q

What enzyme do the host cells not have that single stranded (-)mRNA require?

A

RNA dependent RNA polymerase

53
Q

What are the three things a virus needs to do to successfully multiply

A

Make genome available to the host
Multiply the genome
Multiply the protein components

54
Q

What does DNA polymerase do

A

Use DNA templates to make DNA
DNA-dependent DNA polymerase

55
Q

What does transcriptase do

A

RNA polymerase (transcriptase)
Use DNA templates to make RNA (mRNA,tRNA, rRNA)

56
Q

What do DNA viruses do to get the enzymes they need?

A

Can use host cell polymerase OR can code for their own DNA polymerases and transcriptase

57
Q

How do RN viruses get the enzymes they need?

A

Can use host cell polymerase OR code for their own polymerases OR carry own viral polymerases

58
Q

What type of enzymes can RNA viurses have

A

“RNA-dependent RNA polymerases”

59
Q

What type of enzymes do retroviruses have?

A

Retroviruses (RNA viruses) have reverse transcriptase OR RNA dependent DNA polymerase

60
Q

Two types of host polymerase

A

DNA-dependent DNA polymerase
DNA-dependent RNA polymerase

61
Q

dsDNA double-stranded DNA examples

A

Herpes viruses (Envoloped; common human infection)
Herpes simplex virus (HSV) or human herpes virus (HHV)
HHV-1 & HHV-2 (Cold sores & genetital herpes)
HHV 3 (chickenpox and shingles) - Varicella-zoster virus
HHV-4 (Mononucleosis and cancer)
HPV (Common cause of warts)
HPV-16and 18 (Genetical warts and cervical cancer

62
Q

ssRNA(-) examples

A

Genome: Single-stranded antisense or -ssRNA
Measles virus (evoloped, influenza virus (multiple strands, enveloped), rabies virus (encoloped), ebola virus

63
Q

ssRNA(+)

A

Covid19, rhinovirus, hepatovirus, poliovirus
Can carry RNA dependent RNA polymerase
Some do not carry their own enzyme, but it is coded in their genome to make the enzyme RNA dependent RNA polymerase

64
Q

example of dsRNA

A

Rotavirus

65
Q

What is a retrovirus

A

A unique ssRNA(+) virus that uses reverse transcripase to be converted into DNA and inserted into the host cells genome

this reverse transcriptase is carried by the virus and converts RNA to DNA

66
Q

What are enzymes made of

A

Proteins

67
Q

Where is RNA assembled in the cell

A

Cytoplasm

68
Q

Where is DNA assembled in the cell

A

Nucleus if present, cytoplasm if not

69
Q

Most of the viruses that cause cancer are

A

double stranded ones nad the retroviruses bc the genetic material of the viruses become integrated into the host genome

70
Q

How do cancer causing viruses work

A

Viruses activate parts of cellular genomes called oncogenes
Oncogenic viruses or oncoviruses
Viruses activate these parts of our genes
Activated oncogenese transform normal cells into cancerous cells
Transformed cells have increased growth, loss of contact inhibition, have virus specific antigens on surface called tumor specific transplantation antigens TSTA or T antigens in nucleus

71
Q

Examples of retrovirus

A

HIV-1: AIDS

72
Q

Examples of Oncogenic DNA virus

A

Human herpesvirus
Pappillomavirus cause almost all cervical cancers
Hepatitis B virus

73
Q

Oncogenic RNA viruses

A

Retroviruses
Human T-cell Leukemia viruses

74
Q

Types of viral infections

A

Acute: Sudden onset, e.g. Influenza virus
Latent infections
Virus remains in asymptomatic host cell for long periods
Cold sores, shingles, HIV/AIDS/Leukemia
Recurrent: e.g. shingles
Persistent or chronic infections
Occur over long periods, often fatal
Cervical cancer, Burkitt’s lumphoma, liver cnacer, AIDS

75
Q

Viruses share similar mechanisms to each other, what process may vary?

A

the biosynthetic processes to replicate their nucleic acid and transcribe their mRNA vary.

Some viruses use host cell enzymes (DNA polymerase and RNA polymerase) to replicate their nucleic acid and transcribe their genes, whereas other viruses make use of viral-encoded enzymes. In all cases, it is the host cell ribosomes, tRNAs, and ATP that enable translation of viral proteins.

76
Q

What is the function of the structural elements of a virus?

A

To package and protect the viral genome

77
Q

In which stage does formation of mature viruses occur?

A

Assembly

77
Q

In which stage is the viral DNA introduced into the cell?

A

Penetration

78
Q

The host DNA is usually degraded during which stage?

A

Biosynthesis

79
Q

What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?

A

The virus would not be able to infect new hosts.

80
Q

When the phenotype of a bacterium is changed via ________________
, harmless bacteria can become pathogenic and are able to produce deadly toxins and proteins.

A

Lysogenic conversion

80
Q

Are capsids aquired from the host upon release?

A

No

81
Q

An inactive bacteriophage is a ________

A

Prophage

82
Q

When a bacteriophage infects hosts’ cells and allows them to grow and replicate normally for many generations before lysis, this is considered

A

Lysogeny

83
Q

Temperate phages

A

another name for lysogenic phages that have a lysogenic replication cycle.

84
Q

a phage is excised from the host chromosome via physical or chemical agents that damage the genetic material of the host.

A

Induction

85
Q

What can bring on shingles

A

Stress and old age

86
Q

Major way viruses differ from bacteria?

A

Acellular

87
Q

A feature that may be found in viruses but never in bacteria is

A

May contain an RNA genome

88
Q

Are virus enzymes catobloitic

A

No

89
Q

Why aren’t viruses living

A

Not composed of cells

90
Q

What common bacterial test is NOT used for virus

A

Biochemical tests

91
Q

Are Glycoprotein spikes are found on the capsids of all viruses?

A

No

92
Q

Bacteriophages and animal viruses do not differ significantly in which one of the infection processes?

A

Biosynthesis

93
Q

Lysogeny is the process of:

A

Phage DNA is incorporated into host cell DNA.

94
Q

A viral envelope is acquired during ________.

A

release

95
Q

A virus’s ability to infect an animal cell depends primarily upon the ________.

A

presence of the corresponding binding receptors on the cell membrane

96
Q

What enzyme porudced by the host cell is not used by viruses

A

DNA polymerase

97
Q

Most RNA viruses carry which enzyme?

A

RNA-dependent RNA polymerase

98
Q

RNA viral multiplication process

A

BIO233 (18 decks)

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